When measuring current drawn from a DC power supply, what does the ammeter placed in the circuit appear as?

An ammeter must be connected in series with a circuit to measure the actual flow of electrons (current) passing through it. Because the entirety of the circuit's current must flow directly through the meter, the ammeter is designed to have a very low internal resistance. If an ammeter had a high internal resistance, it would act as a bottleneck in the circuit. This restriction would act as a significant additional load, artificially lowering the amount of current flowing and leading to a highly inaccurate measurement.